Plastic bag



FIG. 1 is a front elevational view of a plastic bag showing my new design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a top front perspective view thereof; and,

FIG. 6 is a bottom front perspective view thereof. 

The ornamental design for a plastic bag, as shown and described. 